Surface Texturing of 40Cr Steel by Heat-assisted Ultrasonic Rolling
Ultrasonic rolling texturing has been proven to exhibit distinctive surface enhancement effects.However,the singular application of ultrasonic rolling encounters challenges when processing materials with high hardness.Furthermore,its ability to enhance the surface performance of materials has an inherent limitation that restricts its further application.To overcome the limitations of ultrasonic rolling texturing,in this study,a heat-assisted ultrasonic rolling technique was employed for micro-texturing preparation on the surface of 40Cr steel.The study aimed to achieve better performance on textured surfaces by using the temperature field to evaluate the influence of temperature on the microstructure and mechanical properties of the material.Additionally,the study evaluated the effect of temperature on the morphological and mechanical properties of ultrasonic rolling-textured surfaces.Before conducting ultrasonic rolling tests,the specimens underwent grinding and polishing and were heated to predetermined temperatures(20,100,150,and 200 ℃).The processing trajectory followed a reciprocating linear path.Additionally,a three-dimensional finite element model was established using ABAQUS software to simulate the ultrasonic rolling process at different temperatures,utilizing the Johnson-Cook model to describe the plastic deformation of the material.The simulation results were compared with the experimental results.The latter revealed that the heat-assisted ultrasonic rolling texturing treatment formed a textured array on the material surface consisting of micro-protrusions and micro-grooves.Heating induced material softening and intensified the degree of plastic deformation on the material surface,resulting in a larger-scale morphology of the ultrasonically rolled textured surface.However,at 200 ℃,material surface damage occurred because of the adhesion between the rolling ball and substrate.The numerical simulation results indicated that heating intensified the material surface work hardening and expanded the range of residual stress generation.The residual stress values initially increased with the depth and then decreased,reaching a maximum value at a depth of 0.1 mm.The cross-sectional morphology analysis revealed that heat-assisted ultrasonic rolling formed a deeper plastic deformation layer.The alignment between the experimental textured surface profiles and numerical simulation results confirm the reliability of the finite element model.The hardness of the material surface generally increased after heat-assisted ultrasonic rolling texturing,and the residual stress state manifested as a residual compressive stress.Both the residual stress and micro-hardness exhibited an initial increase,followed by a decrease with an increase in temperature.The micro-textured surface prepared at 150 ℃ demonstrated optimal comprehensive mechanical performance.The initial increase in the residual stress values with the temperature is attributed to the increased plastic deformation on the material surface due to heating,whereas the subsequent decrease in residual stress is associated with thermal stress relaxation.The initial increase in micro-hardness with temperature was a result of enhanced work hardening on the material surface after heating,whereas the decrease in hardness at 200 ℃ was due to grain growth and organization coarsening after the temperature increase.The XRD test results confirm that the increase in residual stress and micro-hardness is related to the material surface grain refinement caused by heat-assisted ultrasonic rolling.Heating intensified plastic deformation,thereby promoting grain refinement on the material surface.However,the simultaneous increase in temperature led to grain growth and coarsening.The surface prepared at 150 ℃ exhibited the smallest average grain size,indicating the best comprehensive performance for ultrasonic rolling texturing.The research results validate that introducing heating into the ultrasonic rolling texturing process can further improve the material surface performance,providing a novel avenue for the research and application of ultrasonic rolling technology.
ultrasonic rollingsurface texturingthermoplastic forming40Crfinite element simulation
万方数据
维普
